But to answer your question: Cast wave of conflict, and be clanless. You will be put in a clan for next war
You don't sign up for the individual wars with a clan. If you're going to sign up for the individual wars, you need to cast the Wave of Conflict(located in the Alchemist) and be clanless 2 hours before the time the war starts. For the war times, look here. If you still don't understand, wall me and I'll help you out. /lock